Mavalvala was among the team of scientists who, for the first time, observed ripples in the fabric of spacetime called gravitational waves. It was announced to the public on 11 February 2016. The detection confirmed a major prediction of Albert Einstein's 1915 general theory of relativity.[10]

After the announcement of the observation, she became an instant celebrity scientist in her birthplace of Pakistan. Talking to the press she claimed that "we are really witnessing the opening of a new tool for doing astronomy."[16][17]

During an interview with Pakistani newspaper Dawn, after the detection of gravitational waves, she claimed that she was baffled by public interest in her research in Pakistan. She said “I really thought of what I want people to know in Pakistan as I have garnered some attention there. Anybody should be able to succeed — whether you’re a woman, a religious minority or whether you’re gay. It just doesn’t matter.”[11] In a statement by the Prime Minister of Pakistan, Nawaz Sharif, the Prime Minister praised Mavalvala, calling her a source of inspiration for Pakistani scientists and students aspiring to become future scientists. He also stated that "the entire nation is proud of her valuable contribution."[18]

Optical cooling of mirrors to nearly absolute zero can help eliminate measurement noise arising from thermal vibrations.[8] Part of Mavalvala's work focused on the extension of laser cooling techniques to optically cool and trap more and more massive objects, both for the LIGO project and for other applications, such as to enable observation of quantum phenomena in macroscopic objects.[7] Prominent results from her group in this area included cooling of a centimeter-scale object to a temperature of 0.8 Kelvin[7] and observation of a 2.7 kilogrampendulum near its quantum ground state.[8] These experiments lay the foundations for observing quantum behavior in human-scale objects.

Prof. Mavalvala has also worked on the development of exotic quantum states of light, and in particular the generation of light in squeezed coherent states.[9][22][23] By injecting such states into the kilometer-scale Michelson interferometer of the LIGO detectors, her group greatly improved the sensitivity of the detector by reducing quantum noise;[23] such squeezed states also have many other applications in experimental physics.